Stepwise tape transport mechanism



Oct. 11, 1960 E. LEONARD 2,955,321

STEPWISE TAPE TRANSPORT MECHANISM Original Filed March 25, 1956 2Sheets-Sheet 1 VOLTAGE WAVEFORM GENERATOR CONTROL MEANS /N/ T/A T/NGMEANS CURRENT WA l/E FORM GENERATOR 0 0 TRANSPORT MEANS SENSING MEANSTERM/NA TING MEANS Q as IN VEN TOR.

EUGENE L EO/VARD Fla/ m/ A T TORNEK Oct. 11, 1960 E. LEONARD 2,955,821

STEPWISE TAPE TRANSPORT MECHANISM Original Filed March 23, 1956 2Sheets-Sheet 2 W GENERATOR all L cums/v7 WAVEFORQM GENERATOR 43.3

rmus onr MEANS SENSING MEANS 5 2 C5 INVENTOR. CB EUGENE LEONARD "Z$7v I2 W L l United States Patent 2,955,821 STEPWISE TAPE TRANSPORT MECHANISMEugene Leonard, Port Washington, N.Y., 'assignor, by mesne assignments,to Curtiss-Wright Corporation, Carlstadt, N.J., a corporation ofDelaware Continuation of application Ser. No. 573,372, Mar. 23, 1956.This application Dec. 31, 1956, Ser. No.

2 Claims. (Cl. 226-32) This invention relates to tape transportmechanisms in data processors and more particularly to mechanisms whichtransport tapes in a stepwise movement.

Tapes containing control or information indicia are often used in dataprocessors. The tape is moved to a sensing station where a line ofindicia is sensed causing the generation of control or informationsignals that are transmitted to the data processor. The transmission ofthe signals to the data processor causes the data processor to perform astep of a processing operation.

At the end of the processing step the tape is moved and a new line ofindicia is sensed. The stepwise sequential sensing of lines of indiciaon the tape which causes the transmission of signals to the dataprocessor directs the data processor through a complete processingoperation.

Since the time required to perform one processing step is usuallydifferent from the time required to perform others a uniform motion israrely employed to transport the tape. Instead, whenever a processingstep is completed an initiating signal is fed from the data processor tothe transport mechanism to start the movement of tape so that the nextline may be sensed. Upon receipt of the initiating signal the transportmechanism moves the tape.

The transport mechanism includes a stepper motor, that is a motordesigned to move through a fraction of a revolution each time itreceives a command pulsing signal to do so. Even the highest qualitystepper motors are known to fail upon occasion to step or advance, uponreceipt of a command pulse. This phenomenon is somewhat alike tosticking of relay contacts, that is failure of relay contacts totransfer upon change in energization state.

If the tape does not move because of such stepper motor response failurethe same line of indicia is again sensed and the associated processingstep is reperformed. The reperforming of the same processing step maycause a serious error in the overall processing operation.

It is therefore an object of the invention to provide an improved tapetransport mechanism that prevents repetitive sensing of the same line ofindicia on a tape.

To prevent the repetitive sensing of the same line of indicia detectioncircuitry may be employed which would halt the data processor andtrigger an error indicator. Although such apparatus indicates to theoperator that misstep has occurred, it is then necessary for theoperator to restart the data processor and manually initiate the tapemovement. Such operations which are caused by transient misstepping ofthe tape are usually time consuming and consequently slow down theprocessing time appreciably.

It is therefore another object of the invention to pro vide improvedtape transport apparatus which automaticallycorrects the transientmisstepping of the tape.

It is a further object of the invention to provide apparatus for movinga tape in a stepwise manner which upon failing to step the tape asdirected automatically performs another stepping operation.

In accordance with the invention apparatus is provided in data processorfor moving a tape in a stepwise or discontinuous manner. The apparatusincludes a control means having a first and a second state. Means areprovided for setting the control means into a first state. When thecontrol means are in the first state a current generator generates acurrent waveform which causes a motor to rotate a fixed amount. Themotor, in turn, causes a drive mechanism to move the tape a givendistance. i

The drive mechanism includes indicators which respond whenever'the drivemechanism is activated. The controllable sensing of an indicator causesthe control means to return to its second stable state and thusterminate the operation of the current generator. Therefore thetermination of the operation is dependent on the sensing of anindicator. If an indicator senses failure of stepper motor advance, asecond current waveform is fed to the motor and a second attempt is madeto move the tape. 7

It should be noted that the apparatus of the invention permits theautomatic reinitiation of a stepping operation when the first attempt tostep the tape fails.

A feature of the invention is a novel current waveform generator whichfeeds current pulses to the windings of the motor.

Otherobjects, features and advantages become apparent from the followingspecification taken with the drawings wherein:

Fig. l is a block diagram of the apparatus showing the mechanicaloperation of the transport and sensing means in accordance with theinvention.

Fig. 2 is a diagram partially in schematic and partially in symbolicform of the block diagrams of Fig. 1. I

In the drawings,signals are designated by alphabetical characters whichmay be assumed to be merely reference labels for purposes of the presentinvention. For brevity of description a signal and also the linecarrying such signal will be identified by the associated alphabeticalcharacter. The physicalsignificance of these alphabetical characters ina complete electronic digital computer, of which the apparatus of thepresent invention forms but a part, is explained for example incopending applications of Samuel Lubkin for Electronic Calculator,Serial No. 567,566, filed February 26, 1956, now Patent No. 2,945,

' 213 of July 12, 1960 and of Evelyn Berezin for Control Means withRecord Sensing for an Electronic Calculator, Serial No. 567,567, alsofiled February 24, 1956, and assigned to the assignee of the presentinvention, and in my copending application for-Program Device, SerialNo. 573,372, filed March 23, 1956 of which the present application is acontinuation. The apparatus of the present invention may be, and in factis fully incorporated in the computer of the Lubkin and Berezindisclosures, like-labeled signals in the three descriptionscorresponding to one another. However, for brevity of disclosure themeans for generating signals CE, C S, CSD, MH and MH encounteredhereinafter are illustrated. in simplified form. The apparatus of thepresent invention also utilizes recurrent synchronizing timing signalsof the com-. puter of the Lubkin patent. The timer for generating thesesignals is illustrated in Fig. 57 and the timing waveforms in Fig. 58thereof. As shown therein, 44 pulse times constitute one timing cycle sothat t44 of one cycle is 20 of the next cycle; quarter fractions ofpulse times are the lowest units of significance, so that :44 (t0) isdesignated as t44-0/4. One pulse time is of microsecond order ofmagnitude. The timing signals utilized herein are t44-1/4, t44-2/ 4,13-3/ 4, t4-1/4, t41-1/4, occurring in the order named in a given cycle.It should be appreciated that the present invention may be utilized inconjunction with other pulse; The control means 56 is a flip flop whichhas two r ,4 it

. At the same time as the CQ signal is fed, voltage waveform generator58 initiates the generation of, first, the

YA and the YA signals andQthen the YB and the 'YB signals, These signalsare fed .via their associated signal lines to the current waveformgenerator 133; The current waveform generator-133. upon receipt of thesesignalsgeneratescurrent waveforms which are fed via the lines 68 and 70to the motor 129.

The motor .129 attempts to rotate one forty-eighth of acomplete'revolution and move the tape forward by means of the transportmeans 50. Ifthemotor129 and 7 therefore'the transport means 50 rotateproperly, the boss 7 feeler 74 will change position and appropriatevoltages stable 'statesr When thecontrol means 56 receives a .sig-

nal via' a set signal line CE the flip flop is triggered to its stablestate When the control'means 56 receives asignal via a reset signallinelCB the flip flop is triggered to its second stable state.

' The voltage wavefonn generator 58 is essentially a twostagebinarvbounter plusra delay circuit which functions 'to generate aspecified sequence of voltage. waveforms. .These waveforms are fed vialines YA, -YA, YB, 'YB

to fhe currentiwaveform generator 133. The: current i will be generatedin the sensing means 5 2. These voltages are compared with the presenceor absence of a voltage generated by the memory circuit of the sensingmeans 52. Upon a proper comparison positive potentials are generatedthat are fed to the terminating means 62 via a the lines 64. and 66. if-positive potentials are present on V V deactivation of these-two-units.J

waveform generator 133 is primarilya current amplifier which convertsvoltage waveforms to high current waveforms suitable for 'driving thestepper motor 129.

The motor 129 is a multi-pole stepping motor whichi'Qtates-one-forty-eighth of ia complete revolution when it receives oneperiod of the current waveform based on 'the YA and YB signals from the.current waveform generator 133via-1ines 68 and-7.0. The transport means50 isprimarily two sprocket wheels having teeth which enter sprocketholes-of the tape 130 to be transported. On the side of-one of thesprocket wheels is 'a circular array of24bosses 72; i l 1 both of theselines a ,CB' signal is generated by the terminating means 62. The +CBsignal is fedto the sensing means 52 and to the control means 56 to'cause the i If, however, the-rotation of the port means 50is notaccomplished, the boss feeler 74 does not change position andthesensing'means 52-does not transmit positive potentials along both thelines 64 and 66. Therefore the '.-CB signal is not generated and thecontrol rneans 56 is not deactivated. With the .The sensing means 52ispartially mechanical and par tiallyelectrical; It has a .boss feeler74which rides'over the bosses 72 to activate a double-throw switch 1200which; for each step .of the transport means 50 alternates intransferring a positive voltage +5 volts from one to the other of twoinput terminals QD- and OD. of. the

sensing means 52;

. minal cooperates with a memory device (a flipjflop) in the sensingmeans 52 to determine :whether the transport means 50 has rotated;Theterminating means 62 is controlmeans'56 'stfllin anlactivatedcondition, the CQ signal isstill being fed to the voltage waveformgenerator 58 and anew series of voltage waveforms are generated.

. This new series of voltagewaveforms would again cause the attemptedrotation of the transportmeans 50. This operation islrepeated until themotor'129 andtransport means dorotate. I 1 {j Referring toFigureZ,

the initiating means 54, as shown 7 forsimplified illustrativepurposes,comprises the single pole double thr0w switch 150 having the fixedcontacts i The presence of thevol tage i on a particular input ter- 152and 154 and moving contact 156."."1he fixed con tact 152'is returned toa positive five volt potential via a resistor 158. The moving contact156 is returned to a negative ten volts potential via thecondenserj160.

" The fixed contact 154 is returned to the negative tenflvolts basicallya flip flop circuit whichwhen activated feeds I a signal CB to thecontrol means 56 and sensing means [52 to reset the flip flops therein 1The itiating means 254 is coiipled via' the .CE-signal line to asetinput terminal o f the control means 56 and viazthe same CE signal lineto a priming input terminal 7 J of the sensing ;means 52. 'Thecontrolmeans 56-is connected to the :voltagewaveform generator 58 and toterminating'rrieans 62 byr the signal line; The voltage waveformgenerator '58 is also linked to the terminatin means 62 by the YA andthe YB signal lines. 7 v

- sistor 162 causing a positive 'volt'age transient or pulse potential.via a'resistor 162. The: outgoing. CE signal line is alsoconnected tothe fixed contact 154.

i The initiating means 54 operates as follows: The

I moving contact 156 is normally'in contact with the fixed contact152causing the condenser 160 to' be charged to a potential .of plus fivevolts; When the initiating means isactivatedthe moving contact moves tothe fixed contact 154 and the condenser discharges through the re- CE tob e fed to the CE -sign'al line. The engagement of the contacts 154 and156 is momentary; so that prior .to the next CE signal contacts 152 and156 are once "more in engagement. .Thus'the' CE'signal isgenerated Themotor 129 is connected to thetransport means 50 I V by. the s'haft.78.=The transport means 50 is mechanically linked to'the sensing means 52 bymeans'of themecharh ical contact of -the'bosses'72and'the boss feeler74. The

sensing means 52 supplies input signals to the terminating means 62 bymeans of the lines' 64 and 66,. s 7 7' When the tape is to be stepped toa new position the mtiatingmeans 54 is activated." The initiating means54 I feeds'the' CE signal to the eontrol means 56 and sets the flip floptherein to its first stable state. The CEsignal is also ied tothesensing means 52' to prime the associ- V ated' electrical circuitrytherein." 'When the ;-flip flopof the control means 56 is in its lfirststable state .the CQ signal is generated and fed via the CQ signal lineto the mally. moves.

' in the manner illustrated in 'Fig.' 45 of the mentioned Lubkin patent,that is 'it occurs at: t44-0/4 (equivalent to I0). Itsoccurrence'im'tiates a series of 44 pulse' time cycles during which thetransport means 50 nor- The control means'56 comprises'the flop and thefor g'ate 1 68. The 'fiip fiop'166 is an electronic 'circuit havingtwostable statesilts symbolic representa 7 tionsignifies that it is a'reset dominant flip flop? as voltage; waveformjgenerator 158 and to theterminating means 62- 'In response, the terminating means 62'prirneshe-terminating means 62 forthe receipt of signals from thegs'ensing'means 52. JJ 'i' distinguished from the set dominant fiip finalist encountered hereinafter, which hasadistinguishirig symbolicrepresentation. The representations are consistent with thoseused inFigs. 34 and 35 'offthe Lubkin pat- V out, which also illustrate the.internal circuitry of the two fiip'flop types B'riefly'st'ated here; theflip flop 166 has a set terminal 170, a' reset terminal 172, a positiveoutput terminal 174 and a negative output terminal 176.

When the flip 'fiop" 166 receives the positive "CE input motor 129 andtranspulse at its input terminal (the set terminal 170 the flip flop istriggered to its first stable state in which the positive outputterminal 174 transmits the positive potential CQ and the negative outputterminal 176 transmits the negative potential CQ. It remains in suchstate even when the positive input pulse is removed, unless and until itreceives a negative input pulse via its reset terminal 172, whence it istriggered to its second stable state in which the positive outputterminal 174 is at negative potential and the negative output terminal176 is at positive potential. the negative input pulse is removed untilonce more a positive setting input pulse is applied. Upon simultaneousapplication or removal of both input pulses, the flip flop will remainin its second stable state; hence the designation reset dominant. Thepositive output terminal ,174 is coupled to the outgoing CQ signal line.

The or gate or buffer (illustrated in Fig. 26 of the Lubkin patent) 168is a coincidence gate which passes the most positive potential presentat its input terminals. It has a first input terminal 178 coupled to theCB signal line and a second input terminal 179 coupled to a timingsignal line t4l-1/4. Thus the flip flop 166 is reset at a pulse timet41-1/4 with the CB signal then negative.

The voltage waveform generator 58 comprises the setdominant flip flops180 and 182, the and gates (illustrated in Fig. 25 of the Lubkin patent)1'84 and 186, the buffers 1'88 and 190, the delay line (illustrated inFig. 27 of the Lubkin patent) 192 and the delay circuit 60. The andgates 184 and 186 are coincidence gates which transmit the most negativepotential present at their respective input terminals. The setdominantflip flops 180 and 182 are similar to the previously described resetdominant flip flop 166, except in the following respect. When both thepositive set input pulse and negative reset input pulse aresimultaneously applied or removed, the flip flop will remain in itsfirst stable state; hence the designation set dominan. The butters 188and 190 are or gates similar to the previously described or gates. Thedelay line 122 is of the lumped parameter type which will transmit asignal from its output terminal a predeterruined period of time afterthe receipt of the signal at its input terminal.

I The output terminal of the gate 184 is coupled to'the set terminal ofthe flip flop 180. -The output terminal of the buffer 188 is connectedto the reset terminal of the flip flop 180. The positive output terminalof the flip flop 1 80 is connected to the outgoing YA signal line andthe negative output terminal is connected to the outgoing YA signalline. The gate 186 has two input terminals. The first input terminal iscoupled to 21 CSD signal line. The second input terminal is connected tothe YA signal line. The output of the gate 186 is coupled to the setinput terminal of the flip flop 182. The output terminal of the bufier190 is coupled to the reset input terminal of the flip fiop 182. Thepositive output terminal of the flip flop 182 is coupled to the YBsignal line and the. negative output terminal is coupled to the YBsignal line. The delay circuit 60 receives the CQ input signal anddelivers the CS and CSD output signals. It is a circuit which whenprimed by the CQ signal will for the duration thereof generate a seriesof pulse signals that are delayed from each other by times in the orderof milliseconds, and therefore embrace many 44 pulse time periods. Verystable multi-vibrators may be employed. In the computer of the Lubkinpatent, the delay circuit is illustrated in Fig. 40, there designatedStepping Pulse Width Control 1 16b.

The voltage waveform generator 58 operates as follows: The positivepotential CQ generated in response to the CE signal is passed to thedelay circuit 60, activating it, and also to the and gate 184. At thetime of generation of the CE signal, the potential of a second itremains in the second state, even if 6 input signal line YB to gate 184is positive and remains positive for the time being. At t44-2/4 apositive synchronizing pulse is applied to a third input of gate 184.All inputs to the gate 184 being positive, it transmits a positive pulsewhich sets the flip flop and a positive potential is transmitted via theYA signal line and a negative potential is transmitted via the YA signalline. A predetermined period of time of the order of milliseconds (asdetermined by the delay circuit) after delay circuit 60 is primed by thepositive CQ signal, a pulse of negative potential is generated on thenormally positive CS signal line which at this time has no eifect sincethe positive potential on the YB line holds flip flop 180 set. A shorttime thereafter a pulse of positive potential is transmitted via the CSDsignal line to an input terminal of the and gate 186. Since the secondinput terminal of the and gate 186 is coupled to the YA signal line bothinput terminals of the gate 186 are at positive potentials. Therefore, apositive potential is fed through the gate 186 to set the flip flop 182causing the generation of a positive potential on the YB signal line anda negative potential on the YB signal line. At this time both the flipflops are set. After another period of time, a second pulse of negativepotential is again present on the CS signal line. This negativepotential pulse and the negative potential on the YB line acting throughthe buffer 188 cause the resetting of the flip flop 180, rendering thepotential of lines YA and YA negative and positive, respectively. Thenow negative YA potential is passed through delay line 192 to buffer190. As yet flip flop 182 does not reset, since the other CS input tobuffer 19%) is presently positive. After a time delay equal to theprevious time delay a pulse of negative potential is again present onthe CS signal line. This negative potential pulse and the delayednegative potential on the YA line is transmitted through the bufler 190causing the reset of the flip flop 182.

To summarize, initially the presence of the positive potential on the CQsignal line causes the setting of the flip flop 188. The first pair ofsignals out of the delay circuit 60 then cause the setting of the flipflop 182. The second pair of signals out of the delay circuit 60 causesthe resetting of the flip flop 180. The third pair of signals from thedelay circuit 60 then'causes the resetting of the flip flop 182. Thus,it is seen that the flip flops 180 and 182 act as modified binarycounters.

The sensing means 52 comprises the switch 200 having a moving contact202 and the fixed contacts 204 and 206, the resistors 208 and 210, thedelay line 212, the and. gate 214, the buffers :216, 218 and 220, andthe setdominant flip flop 222.

a The moving contact 202 of the switch 200 is returned to a positivefive volts potential. The moving contact 202 is mechanically coupled tothe boss feeler 74 (see Figure v1) which controls the movement of thiscontact. The fixed contact 204 is coupled to the outgoing OD signal lineand the fixed contact 206 is coupled to the outgoing OD signal line. TheOD signal line is returned to a seventy volts negative potential via theresistor 208 and the OD signalline is returned to the same potential viathe resistor 210.

The input terminal of the delay line 212 is coupled to the incoming CEsignal line. The output terminal of the delay line 212 is coupled to oneinput terminal of the gate 214. The second input terminal of the gate214 is coupled to the incoming 0D signal line. The output terminal ofthe gate 214 is coupled to the set terminal of the flip flop 222. Thereset terminal of the flip flop 222 is coupled to the output terminal ofthe buffer 216.

The positive output terminal of the flip flop 222 is coupled to theDO'signal line. The negative output terminal of the flip flop 222 iscoupled to the -DO signal line. The first input terminal of the buffer218 is coupled .to the OD signal line and the-second input termiml ofthe buffer 220 is 62viathe line 64.

7. I nal bfthe bufler 218 is coupled to. the DO signal line;Iheputput'terininal of the. buffer 218 is coupled to the terminatingmeans'62 via the line 66; The first input terminal ofthe butter 220 iscoupled to the DO signal W lines and'the second input terminal of thebutter 22 is coupled tothe 1- 01) signal line. The, output termicoupledto the terminating means I'he'fir'st input terminal of the butter216'is. coupled tot-he 'f-CB signal lineffrom the terminating means 62.'Thesecond input terminal of'the buffer 216 is .coupled to the 7144474signal line to provide synchronous re- 7 setting ofithe flip flop 222when the apparatus is used withfthe'computer disclosed in the abovecited Lubkin patent. Thus the flip flop is reset at a time 144-1/4 Thisoccurs many with the ''CB signal then negative. 44 pulse time cyclessubsequent to the initial cycle cominencing with the generation of theCE signal, as will be seen hereinafter;

.fThesensing means 52 operates as follows: The CE "signal is generated,sigmfying that the tape is to be .moved. Such motion does not beginuntil the'YA signal is generated subsequently,'as will be seenhereinafter.-

, Before such motion begins, the CE signal is fed through thedelay line212 to the gate 214. Assuming that'the' moving contact 202 is connected,prior to'the tape 'movement; to thefixed contact 204, the OD signal lineis 7 the output terminal of the buffer 218 transmits a positivepotential from the DO line and the output terminal of .lthe'bulfer 220also transmits a positive potential from i the. '-OD line or -+5 .volts.These two positivepotentialsjfed via the lines 66Jand 641:0 theterminating means 62indicate that'the transport means 50 has rotated Ifbecause of "stickmg,of the motor 129 the transport means had rotatedthen the moving contact 202 would ,7 .notbetransferred toithe fixedcontact 206 and the OD I signal line'would be at a negative potential.

tivepotential present at an input terminal of the buffer 220inco'njunction with the negative potential present on the DO signal linefeeding a second input terminal of thebtlficr 220 would cause the outputor the buffer 220 to be at a negative potential. The occurrence ofnegative: potential is an indication that the transport 7 5 means 50 hadnot rotated. V V

As will be seen hereinafter'the terminating means 62 This negaatapositive potential and the flip flop 222 will be set.

is fed through the buffer 220 to the line '64...With the existence of apositive potential onboth the lines 64' and 66 once again an indicationis 'given that the trans portrneans' 50 has properly rotated; Again:assuming failure of the motor 129 and transporfmeans 50 to. rotate,contact 202 would continue to engage contact 206, leaving. the OD linenegative. Since the DO .signal is also negative, :bufler 218, ratherthan buffer. 220 in the previous example, transmitsa negative potentiaL;similarly. signifies that transport means 50 had not rotated. a e V VThe terminating means 62 comprises the seven-input and gate 224 and thereset dominant flip flop'226. A first input terminal of the and--gate224 is coupled to the 64 :signal line, a second input terminal to the 66signal =1ine, 'a third input terminal to the YA signal line, a fourthinput terminalto a;z3-'3/4 timing signal line, a fifth input terminal tothe YB signal line, a sixth input terminal to the CQ'signal line, and aseventh input terminal to the CSD signal line. The output. terminal ofthe gate 224 is coupled to the setinput terminal of the flip flop 226. sThe reset input'terminal of. the flip flop 226 is'coupled to the t4-l/4signal line of the computer of the above cited application to provide asynchronized resetting of flip flop 226. 'The positive output terminalof the reset dominant flip flop 226 is coupled to the CB signal line andthe negative output terminal to the CB signal line. The description ofthe operation of the terminatingrneans 62 will be deferred forrpr' iorconsideration of the current waveform.

' moving'contact'29j0. The'fixed contacts 282 and 292 are connected bythe jumper' 294 and are returned to a receives both of the previouslycited positive potentials.

Inresponse thereto, and at a pulse time t3-3/ 4 occurring in a 44 pulsetime period subsequent to the termination iof tape rotation, theterminating means 62 generates a negative potential which is fed via theCB signal line simplicity of disclosure.

to aninput terminal of the bufler 216. This negative potentialcooperates with,.a negative potential from they 144-1/4 signal lineduring the last-mentioned 44 pulse time period tofcause the resetting ofthe flip flop222.

The-next time the tape is to be moved another pulse theigate 214. Againthe tape has not as yet 'moved.

tore a positive potentialexists on the -,DO signal line fand a'jnegativepotential exists on the DO signal line. 7 Asthetrausport means rotatesthe moving contact 202 T "is'transierred to'the. fixed contact 204 and apositive.

potential of +5 yolts'is applied to the OD signal line.

This positivefpotential isfied through the buifer218 to the line 66, butdoes not set the flip flop, as the delayed QEsignal had long agoterminated. At the Sametime i her sit e r nti l r i e w .D signal li e'is fed via-the CE signal line to the delay line 212'through negativeten volt potential. Thefixedcontaots 286 \and 288 are. connectedtogether by the jumper 296 and are.

returned to a positive 'five volt potential. The moving contact 2904scoupled to the MH signal line. The movingcontact 284 is coupled to theMH signal line. Application of 5 volts tdthe MH line and of 10 volts'tothe' MH line connotes presence or oncondition of-the MH and MH sigrialsfThe reversed application of these voltages connotes ,their absencev orcit-condition lt should be appreciated'that the indicated representationof the switch 268 and generation of the'MH and -MH signals. is merely'symbolical, or

The ci1'cuit ;means for generatingthe MH and '-MH';signals for thecomputer of the Lublcin patent are illustrated in Fig. 50 therco'f.

' "The YB and-'MH signal l-ines'ar'e fed into the 'two input terminalsof thegatej307; The YB'and MH signals are'fed into the two inputterminals of the gate 308. A buffer 306 is coupled to receive, asinputs, the

. grid of'a vacuum tube 326 iscoupled to ground through a a l M ohmresistor and'to the anode ofthe vacuum tube 322 through a 10 K ohmresiston' The anode ofthe' vacuum tube 326 is coupleddirectly to apotential of two hundred and fi-fty volts. i

The YB and MH signal lines are fed into the twoinput terminals of thegate 303; and the YB and MH signal lines are fed into the gate 304. Theoutput signals from the gates 303 and 304, the YA signal and a minusfive volt potential are fed to four input terminals of the buffer 302.The output terminal of the bufier 302 is coupled to the control grid ofthe voltage amplifier 324. The voltage amplifier 324 is similar to thevoltage amplifier 322. The anode of the voltage amplifier 324 is coupledto the control grid of the vacuum tube 328 through a condenser andresistor in series. The junction point of the condenser and resistor iscoupled to a negative seventy v'olts potential through a 470 K ohmsresistor. The cathode of the vacuum tube 328 is coupled d.i rectly tothe ground and the anode of this tube is coupled to the cathode of thevacuum tube 326.

A YA signal and a potential of minus five volts are fed into the bufier332. The control grid of the voltage' amplifier 334 is coupled to theoutput terminal of the buffer 332. The voltage amplifier 334 is similarto the voltage amplifier 322. The control grid of the vacuum tube 342 iscoupled to ground through a 1 M ohm resistor and coupled to the anode ofthe vacuum tube 334 through a K ohm resistor. The anode of the vacuumtube 342 is coupled directly to a positive two hundred and fifty voltspotential.

The YA and YB signal lines are fed to the two input terminals of thegate 310. A bufier 336 is coupled to receive at its input terminals theoutput signal from the gate 310 and a potential of minus five volts. Thecontrol grid of the voltage amplifier 338 is coupled to the outputterminal of the buffer 336. The voltage amplifier 338 is similar to thevoltage amplifier 322. The anode of the voltage amplifier 338 is alsocoupled to the control grid of the vacuum tube 348 through a condenserand resistor connected in series. The junction point of the seriescoupled condenser and resistor is connected to ground through a 470 Kohm resistor. The cathode of the vacuum tube 348 is coupled to groundand its anode is coupled to the cathode of the vacuum tube 342 throughtwo fifty ohm resistors connected in series.

The motor 129 contains the stepping winding 333 and a holding winding335. One end of the stepping winding 333 is connected to the anode ofvacuum tube 328 through a 130 ohm resistor. One end of the holdingwinding 335 is coupled to the junction point of the two series coupledfifty ohm resistors. The other ends of the stepping winding and theholding winding are connected together and to a potential of plus onehundred twentyfive volts.

The stepping motor 129 is manufactured by The General Electric Companyunder Model Number 55MY54MB1. The vacuum tubes 348 and 326 may beconsidered to be normally conducting and the vacuum tubes 328 and 342are normally cut ofi. Therefore the presence of a signal at the outputterminal of the buffer 306 (a positive potential) will cause the vacuumtube 326 to stop conducting. The presence of a signal (a positivepotential) at the output terminal of the buffer 302 will cause thevacuum tube 328 to conduct. The absence of a signal (no positivepotential) at the output terminal of the buffer 332 will cause thevacuum tube 342 to conduct. The presence of a signal (a positivepotential) at the output of the buffer 336 will stop the vacuum tube 348from conducting.

In the operation of this unit, if the MH si al is not present the tapewill move in a forward direction. The MH signal is either on or olfdepending upon the direction in which the tape is to move. The YA and YBsignals are generated in the voltage waveform generator 58. Thesesignals orient or step the motor 129 one-fortyeighth of a completerevolution. 7

The time occurrence of the YA and YB signals relative 10 to each otherduring the stepping of the motor is as follows:

First the YA signal appears. Approximately ten milliseconds later the YBsignal appears. Approximately ten milliseconds after the start of the YBsignal the YA signal stops. Thus, the YA signal has a duration of abouttwenty milliseconds. .Approximately ten milliseconds after the ending ofthe YA signal the YB signal stops. Thus, the YB signal has a duration ofabout twenty milliseconds. During the first ten millisecond period, orduring the occurrence of the YA signal only, acceleration of the motor129 occurs. During the second ten millisecond period, or during thesimultaneous occurrence of the YA and the YB signals, deceleration ofthe motor occurs. During the third ten millisecond period, or during theoccurrence of the YB signal only, the motor is brought to a stop.

The values of the electrical components are representa tive only, andare not meantas a limitation, it being understood that components havingother values may besubstituted for the components shown.

Under normal operating conditions the motor 129 will he stepped by theoccurrence of a YA signal. However, it is possible that the motor 129will not be stepped by the occurrence of a YA signal. Therefore, toprevent the generation of spurious results that can be caused by thenon-movement of the motor in response to the YA signal, a sensing means52 has been incorporated to sense the movement of the program steppingmotor. If the motor does not step at the first occurrence of the YA andYB signals, these signals will be regenerated until the motor steps.

A switch 200 having a movable contact 202 and two fixed contacts 204 and206 is activated by the movement of the transport means 50, as describedabove. Each step position of the transport means 50 causes the movablecontact 202 to move up or down to contact the stationary contacts 204 or206. Thus if the switch is initially in the position as shown, themovement of the transport means 50 will reorient the movable contact 202to the up position to contact the stationary contact 204; and the nextstep position of the transport means 50 will orient the movable contact202 to-the down position to contact the stationary contact 206. Thestationary contacts 204 and 206 are coupled respectively to the +OD andOD signal lines.

The YA and YB signals that step the control belt 130 are generated inthe voltage waveform generator 58 under the control of the presence of aCQ signal. The

YA and YB signals will be continuously generated as long as the CQsignal is present. The CQ signal is initiated in the control means 56 bya CB signal. The CQ signal is terminated in the control means 56 by thegeneration of a CB signal in the terminating means 62.

The CB signal is generated at the termination of a cycle of YA and YBsignals provided one of the two following conditions is satisfied afterthe motor 129 and transport means 50 have rotated:

(1) The flip flop 222 is set and therefore signal D0 is positive andbuffer 218 transmits positive potential to line 66; and the movablecontact 202 of the switch. 200 is in contact with the contact 206, andtherefore the OD line carries positive potential, and therefore buffer220 transmits positive potential to line 64; or

(2) The flip flop 222 is reset, and therefore signal D0 is positive andbuffer 220 transmits positive potential to line 64; and the movablecontact 202 is in contact with the stationary contact 204, and thereforethe OD line carries positive potential, and the bufier 218 transmitspositive potential to line 66.

To describe the sequence of events during operation it will be assumedthat towards the end of a cycle of YA and YB signals when the transportmeans 50 is stopping at a new position, the flip flop 222 is in a setcondition and the movable contact 202 is in contact with the sta-'tionary' contact 20.6.

doesnot pass to the gate 214.

' a: new position.

The aboveifirst'. conditions are sat now'be consideredl It'will beassumed that the movable isfied, and lines 64 and 66 will apply positivepotentials a to thegate 224'in' theterminating means; The'o'tlier inputsto the gate 224 will immediately or subsequently receive positivepotentials. Thus the input lines -YA and 'YB will carry'positivepotentials inview of the completion of the cycle of YA and YB signals.The CQ line will still continue to carry the positive potentialitcontact '202 is in contact with the stationary Contact 2 04 and a'computer operation is beingftennmated. Therefore the .CE signal-isgenerated which initiates the received at the time of the setting'offlip flop 166 due to V 7 generation of the last previous CEfsignal.Theinput line.

CSD will receivea'positiye potential following'the last precedingnegative CS signahwhich had terminated the YB signal by resetting flipflop 182. i Finallyjat the next t3-3/4 the remaining, like-labeled inputline will receive a positive synchronizing potential. The gate224-transmits 'a positive setting potentialto the flip flop 226. The iCB'signal is generated. It is applied to the bufiers 216 and 168 toprime them for resetting of the flip flops 222 and 166. Such resettingoccurs at thenext 241-1/4 with application of the t41-1/4 synchronizingpulse to the buffers 216 and 166. TheiDO signal terminates. Also j theCQ signal terminates, and as aconsequence the generation of the -CS andCSDsigna'lsi terminates. 1 Finally at the next t4-'l'/ 4 a reset pulseisapplie to flip flop 226, terminating the .'CB signal.

' The computer of the above cited Lubkin patent'" now performs anoperation designated byrthenew position of the tap'e in response to thetermination of the CQ j signal. At the. end of the operation'another CEsignal the computer. The CE signal fed to an inputterminal'of the gate214 via delay line 212, attempts to set the flip flop 222; however theOD signal feeding a secondfinput to the gate 214 is at a negativepotential and a setpulse the state of the flip flop 222 leaves line 66at a positive pm tential and line 64 at a negative potential. This doesnot satisfy the first ofthe two conditions normally required at thisstage to'generate the CB signal as the gate 224 is now unabletoset'flip. flop 226; and incidentally also fails to satisfy'the'secondcondition; The ."CB signal is therefore'not generated and' consequentlythe CQ signal a which initiates a CQ signal is automaticallygene'rated'by 1.

is not terminated,'nor is the flip flop 222'res et. The continuedpresence of the CQ signal prevents the per-' formance of a new operationby the computer, including generation of the next 'CE signal. It thusprevents reperformance of the previous proces'singstep. 'It causes thegeneration-of the YA and YB signals for asecond time. T hesesignalsagain attempt to move the, transport means 50. If the transport meansmovesjas a result of this attempt the first condition for generating the-CB signal will be satisfied andnor'mal operation will again 7 beinitiated. 'Thuseach time the YA andYB signals are The CQ signal causesthe generation of the YA and 'YB signals and-the transport means 50 nowstarts step f ping to a new position. In the courseof stepping to thenew position the movablecontact 202 of the switch 200 'i is'transferredfrom the stationary contact' 266 to the- "stationary contact 204.Towards the end of this'YA and YB signal cycle it is seen that the flipflop' 222 is reset and the m0vable'contact 202 is in contact'with thestationary contact 204 to satisfy the second condition.

1 The entire set of'events is repeated, except that the-flip flop 222 isnot newly reset, having been reset initially. ,Thus, the CB signalin'the terminating means 62 is gen-' erated. The -.CB signal terminatestheCQ signal and the tape is at'its newposition; The computerthenprocceds to perform the operation as directed 'by the tape."

Atflthe end of thisfoperation another-"CE signal is auto-jifmaticallygeneratedi The CE signal causes the generav 'tionfof theC Qsignal. HThe CE signal is also fed to an input terminal of the gate 214.Since the movable conare responsive; V 7 It 'is 'readily seen generatedthe motor 129 will step one position. However, if themotor 129 does'notcause a step when the .QYA and YB signalsare generated, these signalswill be regenerated untilithe motor 129 transport means 50 l thati'asimilar regeneration of YA and YB signals will' occurin'the'alternateset of circumstancesof failure of response of the motor129 and transport means 5th Herewebeginwith engagement 'of the contacts202 and 206;; 'fThlS places-positive potential on line 66 carriesnegativepotentialfThe motor '129'sho uld move at the termination 'of'thefirst set of YA and YB 1 signals; this wonld also plaee'positivepotential on line" 66. This"does-.not. happen for failure of the m otorto tact 202 is; in contact with the stationary contact 204 the'OD signalfed'to-the second input terminal of the gate 214"is positive and theflip'flop 222 is set. i

The C) i'sig'nal causes' its' usual generation ofthe YA and YB signalsand the transport means 50 is stepped to During the steppingto then'ewen. f

tion, the movable contact 202 transfers to contact the stationarycontact 296. At the end of the YA and the YB signals itjis seen that theflip flop222 is set and the j movable contact 262 of the switch 200s incontjact with 'the stationary contact 206 and the first condition forgencrating a -CB signal is once more satisfied. j These op-jerationswillcontinue as the tape is 'steppedfrom one position to anotherposition. If during one of the'stepping. V

operations the transport means 50 therefore the tape 'does not moveafter the generation of the YA and the YB signals, it then becomesnecessaryio regenerate; these.

signals.

a i The conditions in' which the program steppingfmotor was notresponsiveto the YA'and' the'YlB will respond; 'Thusthe second-conditionis violated, signal 'CB is not generatedsignals -.C Q;.CSD, YA'and'YB'go through a second 'cycle'and :rpeated cycles until the 'motorresponds.Again false reperformanceof thepre- 'vious instructions an dffalsegenera tion of the CE signal are prevented; 7

As will-be evident from the foregoing description, .cer'-' tain aspectsof this invention'are not limited to the particular details set'forth-as an example; and is contemplated that various" and othermodifications and applications of the invchtiomwill occur to thoseskilled in the 'It is therefore intended thattheiappended claims shallcover such modifications andapplications as do not depart from the truespiritand scope of the invention. What is claimed as rnew'and is desiredtoh'e secured by Letters Patent of the jUnited'States'is: 1 V

1.-In a data processor controlled by signals; from a 7 moving tape,apparatus for reversiblymoving' said tape' in a stepwise mannercomprising a vbi-stalole electronic flip flop having a first and .asecond state and normally being in said second stat'e initiating meansfor switching 70. said flip flop to said first stable state, electronicterrninafl ing means providing upon activation a pulse of'p'redeterminedduration effective to reset said flip'flop tothe second' stable state,an electronic current waveform generaa tor for generating a'p'eri'odically recurring currentwavej form of current pulses'ofr'p'redeterm'ined duration and 5" pulse separations'of predeterminedduration,- said current waveform generator operating when said flip flopis in said first stable state, a bidirectional stepper motor responsiveto pulses generated by said current waveform generator, said motorrotating a predetermined fraction of a revolution for each pulsewaveform from said current generator, means switchable to effectrotation of said motor in either direction, a tape transporting meanscoupled to said motor, said tape transporting means moving said tape,indicating means associated with said tape transporting means, saidindicating means comprising a plurality of indicators corresponding innumber to the number of steps per revolution of said motor, and sensingmeans cooperating with said indicators to reflect that said motor hasrotated a fractional revolution step in either direction and includingmeans responsive to such reflection for activating said terminatingmeans, whereby upon failure of such reflection said motor continues toreceive pulses from said current generator until such reflection occurs.

2. Apparatus according to claim 1, wherein the sensing means includesswitching means transferable from a first switching state to a secondswitching state with each oddnumbered step movement of the aforesaidmotor and transport means, and vice versa with each even-numbered step,in either direction, and voltage producing means responsive to saidswitching and initiating means to pro Vide one combination of outputpotentials reflecting that the motor has stepped properly and othercombinations of output potentials reflecting failure to step, theterminating means being activatable only upon receipt of said onecombination of output potentials.

References Cited in the file of this patent UNITED STATES PATENTS1,437,949 Sherman et a1 Dec. 5, 1922 1,858,049 Johnston May 10, 19322,113,165 Young Apr. 5, 1938 2,212,653 Steward Aug. 27, 1940 2,787,464Davidson et a1. Apr. 2, 1957 2,791,422 Baer May 7, 1957

